For the purposes of the present description, by electrical apparatus we mean, in general, any means or electrical device generally forming part of electric installations in civil buildings and the like and usually intended to be mounted, for example built in, onto walls of such buildings.
This definition therefore includes, not limitingly, switches, electrical power sockets, sockets for data networks, TV sockets, telephone sockets, buttons, commutators, deviators, electrical adjustment devices in general, connectors, thermostats, timers, fuse-boxes, alarms/buzzers, emergency lights (for example removable), indicator lights (for example guidance lights), displays (for example LCD) and the like.
As known, many of the aforementioned electrical apparatuses are usually installed on a wall using composite mounting structures, or groups of parts, generally including:                a box intended to be built into the wall;        a apparatus-carrying mounting frame (or support frame) that can be fixed to the box and comprising a frame body extending around an opening defining a mounting seat suitable for receiving and holding one or more electrical apparatuses; and        a cover plate that can be fixed to the frame and provided with an opening to allow a user to gain access, visually or manually, to the electrical apparatuses installed on the support frame.        
There is a great requirement to make a mounting group that allows a user to easily identify it even in poorly lit locations.